OnScreen Particle Physics™

The OnScreen Particle Physics™ Detection
Chamber

Subatomic particle decay events unfold in space and time in the simulated
detection chamber. The events are realistic from the standpoints of particle
behavior and detection. The color and 3D graphics grab students immediately.
The chamber and this event are described below.

In the event displayed
above, a neutral pion (invisible since only charged particles can
be seen
) has entered the chamber and decayed into two photons (also
invisible). Each photon has then produced an electron-positron pair. The
direction of the magnetic field is indicated by the green axis. Electron
tracks are shown in red; positron tracks in yellow. Note the opposite sense
of curvature for the oppositely charged particles. Injected particle always
moves in the plane indicated by brick-red outline.

With the real program you can see the tracks traced out in slow motion,
so it's obvious that a matter-antimatter pair originates from a single point.
The helical geometry of the tracks also become obvious when you rotate
the chamber (about any of its three axes) to view it from different perspectives
.
Neutral pions are one of six types of particle that can be selected for
observation in the chamber. The others are charged pions and muons and the lambda particle.

This or any event occurring in the chamber can be seen in projection
views
as well.
These are more like the bubble chamber photographs
you may be familiar with. It is in the projection views that you can measure
distances that enable you to determine particle masses.

The user controls the kinetic energy of the injected particle, the chamber
size, and the magnetic field strength. Thus students can adjust the experimental
conditions based on their observations. Click here
to see the controls.